Liquid crystal display

ABSTRACT

A liquid crystal display includes a liquid crystal display panel which has first and second drain lines groups, a control circuit board which has a control unit, a first and second drain drivers groups connected to the corresponding first and second drain lines groups, a back light unit, a metal frame, and a shield member which shields against EMI. Both of the first and second drain drivers groups are arranged at a same peripheral side of the liquid crystal display panel. The control unit supplies first and second signals to the drain drivers groups via flexible printed circuits which are connected to the control circuit board. The control circuit board is sandwiched between the metal frame and the shield member, and the metal frame is arranged between the control circuit board and the liquid crystal display panel.

CROSS-REFERENCE TO RELATED APPLICATION

This is a continuation of U.S. application Ser. No. 09/987,465, filedNov. 14, 2001 now U.S. Pat. No. 7,077,543, which is a continuation ofU.S. application Ser. No. 09/449,835,filed Nov. 26, 1999, now U.S. Pat.No. 6,331,064, the subject matter of which is incorporated by referenceherein.

BACKGROUND OF THE INVENTION

The present invention relates to an liquid crystal display device. Morespecifically, the invention relates to a back light unit for a liquidcrystal display panel.

A liquid crystal display panel is comprised the pair of opposedsubstrates and a liquid crystal layer interposed between the pair ofsubstrates, wherein an array of pixels is formed in a horizontal planeof the liquid crystal display panel. In this case, a back light unit isneeded, and such a back light unit is arranged in the back of the liquidcrystal display panel. Thus, each pixel has only the function to controlthe amount of light switching by controlling the orientation of theliquid crystal molecules.

This back light includes a lamp tube, a diffusing plate and a reflectorfor supplying the light and uniformalizing the light irradiation of aliquid crystal display panel. A cold cathode fluorescent tube (CFL),whose length is almost equal to the length in a parallel direction ofthe liquid crystal display panel and which is supplied with a voltage byelectrodes attached at both ends of the tube, is used as the lamp tube.

However, a liquid crystal display unit's life span is determined by alamp tube's short life span. Although replacement of the lamp tube inthe back light unit is not easy, all lamps should be replaced tomaintain the brightness of the back light unit.

In addition, an electrode material inside the cold cathode fluorescenttube tends to adhere on the inner wall of the lamp tube due tosputtering which occurs while lighting, and so the lamp tube tends tobecome dark more and more due to the adhesion materials over time. Thatis, the adhesion materials become an alloy (amalgam) of the mercuryinside the cold cathode fluorescent tube, and so the lamp tube's lifespan shortens more and more by consuming mercury.

SUMMARY OF THE INVENTION

The present invention was accomplished in recognition of the aboveproblems, and, accordingly, it is an object of the present invention toprovide a liquid crystal display panel in which the liquid crystaldisplay unit's life span can be increased without the need to replacethe lamp tube or the back light unit.

The above objects are achieved by a liquid crystal display devicecomprising a liquid crystal display panel for modulating light to forman image, and a back light unit having a lamp tube which is dischargedby an electrode and is disposed behind said liquid crystal displaypanel, wherein said electrode is formed outside of said lamp tube.

Further, the above objects are achieved by a liquid crystal displaydevice comprising a liquid crystal display panel having a pair ofsubstrates, a liquid crystal layer interposed between said pair ofsubstrates, and a back light unit having a lamp tube which is dischargedby a pair of electrodes and is disposed behind said liquid crystaldisplay panel, wherein said pair of electrodes are formed outside ofsaid lamp tube and are disposed opposite to each other.

Further, the above objects are achieved by a liquid crystal displaydevice comprising a liquid crystal display panel having a pair ofsubstrates, a liquid crystal layer interposed between said pair ofsubstrates, and a back light unit including a plurality of lamp tubeswhich are discharged by a pair of electrodes comprising a power supplyelectrode and a ground electrode which are disposed at a locationopposite to a display area of said liquid crystal display panel, whereinsaid pair of electrodes are formed outside of said lamp tube and areformed opposite to each other.

Further, the above objects are achieved by a liquid crystal displaydevice comprising, a liquid crystal display panel for modulating lightto form an image, a back light unit including a plurality of lamp tubeswhich are discharged by a plurality of electrodes, wherein saidelectrodes are formed on said lamp tubes, and one of the electrodes isformed between a pair of electrodes.

Further, the above objects are achieved by a liquid crystal displaydevice comprising, a liquid crystal display panel having a pair ofsubstrates, a liquid crystal layer interposed between said pair ofsubstrates, and a back light unit having a lamp tube which is dischargedby a power supply electrode and a ground electrode formed outside ofsaid lamp tube, wherein said lamp tube has an elbow-shaped bend and isdisposed at a location opposite to a display area of said liquid crystaldisplay panel.

Further, the above objects are achieved by a back light unit to supplylight for a liquid crystal display panel, which back light unitcomprises a lamp tube which is discharged by a power supply electrodeand a ground electrode formed on a surface of the outside of said lamptube, wherein said power supply electrode is positioned on the centralportion of said lamp tube.

Further, the above objects are achieved by a back light unit to supplylight for a liquid crystal display panel, which back light unitcomprises a lamp tube which is discharged by a power supply electrodeand a ground electrode formed on a surface of the outside of said lamptube, wherein said power supply electrode and said ground electrode aredivided into two or more pairs, and said power supply electrode or saidground electrode are disposed side by side with respect to each other.

According to the constitution of this invention, the liquid crystaldisplay unit's life span can be increased without changing the lamp tubeor the back light unit.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of essential portions illustrating a liquidcrystal display panel;

FIG. 2 is an exploded perspective view illustrating a liquid crystaldisplay module;

FIG. 3 is a plan view of essential portions illustrating a pixel andperipheries thereof in a liquid crystal display unit of an activematrix-type liquid crystal display;

FIG. 4 is an exploded perspective view illustrating the back light unit;

FIG. 5 is a perspective view illustrating the lamp tube in the backlight unit;

FIGS. 6A and 6B are longitudinal and cross sectional views of a lamptube in a back light unit, respectively;

FIGS. 7A, 7B and 7C are graphs illustrating the relationships among thebrightness of the back light unit and the distance from the center tothe edge of the lamp tube;

FIGS. 8A and 8B are a plan view and a sectional view, respectively,illustrating the back light unit;

FIG. 9 is a graph illustrating the relationships among the averagebrightness of the back light unit and the frequency of a power supplyunit;

FIG. 10 is a perspective view illustrating the resin frame of the upperside of the back light unit;

FIG. 11 is a plan view of the underside of the back light unit;

FIG. 12 is a front view and FIGS. 12( a) to 12(d) are side views of theliquid crystal display panel;

FIG. 13 is a sectional view of the liquid crystal display panel ofembodiment 2;

FIGS. 14A(1), 14B(1) and 14C(1) are sectional views taken on lines 14a(1)-14 a(1), 14 b(1)-14 b(1) and 14 c(1)-14 c(1) in FIGS. 14A, 14B and14C, respectively;

FIGS. 15A, 15B, 15C and 15D are plan views illustrating electrodearrangements of the lamp tube of embodiment 4;

FIGS. 16A, 16B, 16C and 16D are plan views illustrating electrodearrangements of the lamp tube of embodiment 4;

FIGS. 17A, 17B and 17C are plan views illustrating the electrodearrangements of the lamp tube of embodiment 5;

FIG. 18 is an exploded perspective view illustrating the back light unitof embodiment 6;

FIG. 19 is an exploded perspective view illustrating the back light unitof embodiment 7;

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Further objects and features of the present invention will becomeobvious from the following description when taken in conjunction withthe drawings.

<A Liquid Crystal Display System>

FIG. 1 is a plan view of essential portions of a liquid crystal displaypanel. FIG. 1 is drawn corresponding to an actual geometricalarrangement. This embodiment illustrates an In Plane Switching (IPS)mode liquid crystal display with a wide viewing angle.

A liquid crystal display panel 1 is composed of substrates 1A, 1B and aliquid crystal layer interposed between substrates 1A, 1B. In this case,the substrate 1A is formed to be larger than the substrate 1B. Substrate1A and 1B are arranged so that the lower side and right side almostmatch, as shown in FIG. 1. As a result, the left side and upper side ofthe substrate 1A form extended free areas compared with the substrate1B, and a gate driver 15 and a drain driver 16 are formed on theseareas.

A plurality of pixels are arranged in the form of a matrix in the areawhere each of the substrates 1A, 1B overlap. A typical pixel 2 has agate line 3 extending in the direction x of FIG. 1 and arranged in thedirection y, and a drain line 4 extending in the direction y of FIG. 1and arranged in the direction x. This pixel 2 has a switching elementTFT switched by at least supplying timing data through a gate line 3,and a pixel electrode supplied with image data through a drain line 4and a TFT. In addition, each pixel 2 has a counter electrode and astorage capacitor Cstg, since this embodiment's display operates in theIn-Plane Switching mode. And, the left edge of each gate line 3 extendsoutside the substrate 1B and is connected with the output terminal of agate driver 5 formed on the substrate 1A.

In FIG. 1, two or more gate drivers 5 are formed. The gate lines 3 aredivided into plural groups disposed adjacent to each other, and thesegroups are connected to a respective adjoining gate driver 5. Moreover,the upper end of each a drain line 4 is extended outside the substrate1B and is connected with the output terminal of a drain driver 6 formedon the substrate 1A. In this case, similarly, the drain lines 4 aredivided into plural groups disposed adjacent to each other, and thesegroups are connected to a respective adjoining drain driver 6. On theother hand, the gate drivers 5 and the drain drivers 6 may be formed ona printed circuit board 10 (a control circuit board 10) which isdisposed adjacent to the liquid crystal display panel 1.

A control unit 12 which is provided to supply the input signal to a gatedriver 5 and a drain driver 6 is formed on the printed circuit board 10,in addition to a power supply circuit 11. And, the signal from thiscontrol unit 12 is supplied to the gate drivers 5 and drain drivers 6through a flexible printed circuit (a flexible printed gate circuit 15and a flexible printed drain circuit 16A and 16B). That is, a connectionterminal is opposed to each input of a gate driver 5, and the flexibleprinted circuit (the flexible printed gate circuit 15) is connected withthe connection terminal. A part of the flexible printed gate circuit 15is overlapped on the control circuit board 10, and the overlappedportion is connected with a control circuit board on the board 10through a connection port 18. The output signal from a control unit 12formed on the control circuit board 10 is output to each gate driver 5through the wiring layer on the control circuit board 10, the connectionport 18 and the flexible printed gate circuit 15.

Moreover, a connection terminal is opposed to each input of a draindriver 6, and the flexible printed circuits 16A and 16B are connectedwith the connection terminal. A part of the flexible printed draincircuits 16A and 16B are overlapped on the control circuit board 10, andthe overlapped portions are connected with a control circuit board 10through connection ports 19A and 19B. The output signal from a controlunit 12 formed on the control circuit board 10 is output to each draindriver 6 through the wiring layer on the control circuit board 10, theconnection ports 19A and 19B and the flexible printed drain circuits 16Aand 16B.

The flexible printed drain circuit is divided into flexible circuits 16Aand 16B, as shown in FIG. 1, for the sake of preventing heat expansionwith the increase in length in the direction x caused by enlarging theliquid crystal display panel 1. And, the output from the control unit 12is input to a drain driver 6 through the connection ports 19A and 19B ofthe flexible printed drain circuits 16A and 16B. In addition, the imagedata is input from the image data source 22, via a cable 23 and aninterface 24, to the control unit 12.

The liquid crystal display panel 1, the flexible printed gate circuit15, and the flexible printed drain circuits 16A, 16B, along with thecontrol circuit board 10, are flatly arranged in FIG. 1, however thesecircuits can be bent at right angles to the liquid crystal display panel1 for reducing the display frame area outside the display area of theliquid crystal display panel 1. Reducing the display frame areacontributes to the ability to extend the display area.

<A Liquid Crystal Display Module>

FIG. 2 is an exploded perspective view illustrating a liquid crystaldisplay module. The liquid crystal display module is composed of aliquid crystal display panel 400, a back light unit 300, a lower resinframe 500, an inner frame 700, and an upper frame 800. In thisembodiment, a back light unit 300 and a reflector are formed on thelower resin frame 500. Moreover, it is possible for the lower resinframe 500 and the back light unit 300 to be molded as one. In that case,the lower resin frame 500 and back light unit 300 are able to befunctionally distinguished, though they are difficult to be physicallydistinguished.

<A Liquid Crystal Display Panel>

The liquid crystal display panel 400 is composed of the gate drivers 5,the drain drivers 6, a liquid crystal display panel 1, the flexibleprinted gate circuit 15, and the flexible printed drain circuit 16 (16A,16B). The output from a control circuit on the circuit board 10 is inputto a gate driver 5 and a drain driver 6 through the flexible printedgate circuit 15 and the flexible printed drain circuits 16A, 16B. Theoutput of a respective driver is input to a gate line 2 and a drain line3 of the liquid crystal display panel 1. Here, a liquid crystal displaypanel 1 is composed of a plurality of pixels arranged in a display areain the form of a matrix. The arrangement of each pixel is shown in FIG.3. A gate line 3 and a counter signal line 50 are formed in thedirection x on the surface of the substrate 1A. And, the area enclosedby adjacent drain lines 2 formed in the direction y and the lines 3 and50 form a pixel area.

The counter electrode 50A is formed of three parallel counter electrodemembers which do not connect with a gate line 3. Both side counterelectrode members are disposed adjacent to a drain line 3, and theremaining counter electrode member is formed at the center of the pixelarea. A gate line 3, a counter signal line 50, and a counter electrode50A are formed on the surface of the substrate 1A, and these lines arecovered by an insulated layer which consists of silicon nitride (SiN)for instance. The insulated layer is disposed between layers of a drainline 2, a gate line 3 and a counter signal line 50, and functions as agate insulated layer for a thin-film transistors TFT, and in thecapacity Cstg it functions as a dielectric substance film. Thesemiconductor layer 51 is formed adjacent to a drain line 2 on a gateline 3 in the area where the thin-film transistors TFT is disposed onthe surface of the insulated layer, and it consists of amorphous siliconfor instance. The details of the thin-film transistors TFT and the useof a black matrix are disclosed in U.S. Pat. No. 5,754,266.

<A Back Light Unit>

FIG. 4 is an exploded perspective view illustrating the back light unitaccording to this invention. The back light unit 300 is arranged in theback of the liquid crystal display panel 400. The back light unit 300 isreferred to as a direct back light type. The light sources 35 arearranged in the direction x of FIG. 4, are arrayed in parallel in thedirection y of FIG. 4, and are spaced at equal intervals from each other(In FIG. 4, there are eight light sources).

The reflector 36 is arranged between the light sources 35 and the lowerresin frame 500 for irradiating light from the light sources 35 onto theliquid crystal display panel 400. The reflector 36 is formed to have awave-like configuration in the direction y of FIG. 4. The part wherelight sources 35 are formed is concave and a convexity is formed betweeneach of the light sources 35. The reflector 36 is formed to an efficientshape to cause more light from each light sources 35 to be irradiatedonto the liquid crystal display panel. In this case, the opposite sides37 of the frame 500 have slits 38 spaced in the direction y of FIG. 4.The opposite ends of each light source 35 are set in oppositely disposedslits 38, which prevents the light sources 35 from shifting in thedirection y.

In this example, six electrodes are arranged on each discharge tube 35and are spaced on the discharge tube 35 in the direction x of FIG. 4 atintervals. Each electrode is composed of a ring of aluminum foil. Adischarge tube 35 is inserted in the rings which form those electrodes.In embodiment 1,the electrodes are not fixed to a discharge tube 35.Therefore, each electrode can move in position in the direction x ofFIG. 4. Each electrode is mutually connected by a conductive line whichis supplied the ground potential or the power supply voltage. That is,the respective electrodes of the light sources 35 which are aligned inthe direction y are connected together so as to be supplied with asuitable voltage.

FIG. 5 is a perspective view illustrating a lamp tube are used in theback light unit. The ground potential electrodes 35 d are formed at thecenter of a discharge tube 35 a and at both ends thereof, and the highvoltage electrodes 35 c are formed between them. The ground potentialelectrodes 35 d(2) and 35 d(3) are electrically separated and groundedthrough a conductive wire.

FIG. 6A is a longitudinal sectional view of a lamp tube in the backlight unit. FIG. 6B is a sectional view of FIG. 6A taken on the line 6b-6 b. Glass tube 35 p is a cylindrical glass tube having both endsclosed, and is 2.6 mm in outside diameter, 2.0 mm in inside diameter,and 390 mm in length for instance. A fluorescent material 35 q is spreadon the inner wall of glass tube 35 p, and a Ne+Ar (5%) mixture gas andmercury with a gas pressure 60 Torr are enclosed in the glass tube 35 pfor instance.

The 800 Vp-p high cycle sine wave voltage of several MHz (1.5 MHz ormore) is applied by the light sources 35 to the high voltage electrodes35 c. As a result, an electrical discharge is generated in a dischargetube 35 a and activates the fluorescent material 35 q, so thatultraviolet rays and visible light are generated. This electricaldischarge is generated between the ground potential electrode 35 d(1)and the high voltage electrode 35 c(1), between the high voltageelectrode 35 c(1) and the ground potential electrode 35 d(2), betweenthe ground potential electrode 35 d(3) and the high voltage electrode 35c(2), between the high voltage electrode 35 c(2) and the groundpotential electrode 35 d(3).

It is not the high voltage electrodes 35 c, but the ground potentialelectrodes 35 d, that are arranged at both ends of a discharge tube 35a. As a result, an improvement in the efficiency of the electricaldischarge can be achieved. The reason for this is that the high cycleelectric field on the edge of a discharge tube becomes useless, when thehigh voltage electrodes 35 c are arranged at both ends of a dischargetube 35 a. That is, only half of the electric field contributes to theelectrical discharge with such an arrangement. Thus, the groundpotential electrodes 35 d are arranged at both ends of a discharge tube35 a for avoiding a waste of energy.

Moreover, the ground potential electrodes 35 d are arranged at thecenter of a discharge tube 35 a in the form of electrodes 35 d(2) and 35d(3). The reason for this is that the electrical discharge is stronglycaused between one of the high voltage electrodes 35 c(1) or 35 c(2) andthe ground potential electrode 35 d, when the ground potential electrodeat the center is composed of one electrode. Therefore, the groundpotential electrode arranged at the center between two high voltageelectrodes is divided to pair with each high voltage electrode to ensurethat the electrical discharge will be uniform.

FIGS. 7A, 7B and 7C are graphs illustrating the relationships among thebrightness of the back light unit and the distance from the center tothe edge of the lamp tube. A discharge tube having a length of 390 mmwas used. The arrangement of the electrodes was like that shown in FIG.5. FIG. 7A shows a case using 800 Vp-p, FIG. 7B shows a case using 900Vp-p, FIG. 7C shows a case using 1000 Vp-p. Almost uniform brightness isascertained from FIGS. 7A, 7B and 7C, excluding the area near theelectrode.

FIGS. 8A and 8B are a plan view and a sectional view, respectively,illustrating the back light unit. FIG. 8B is the sectional view of FIG.8A taken on the line b-b. The eight light sources 35 extend in thedirection x of FIG. 8A and are arranged in parallel in the direction yat almost equal intervals in the back light unit 300, which is disposedopposite to the liquid crystal display panel 400. In this case, thelight irradiation is not uniform in the area between the light sources,or in the area which is formed by the electrodes. However, thisinconvenience can be canceled by use of a diffusing plate 60 arrangedbetween the back light unit 300 and the liquid crystal display panel400. Moreover, the diffusing plate 60 can change the means which makesat least the illuminance of light from a back light onto the liquidcrystal display panel more uniform.

FIG. 9 is a graph illustrating the relationships among the averagebrightness of the back light unit and the frequency of a power supplyunit. FIG. 9 shows that brightness improves by increasing the frequency.In the back light unit 300 of embodiment 1,since the electrodes arearranged outside the discharge tube, mercury inside the tube is notconsumed. Therefore, light sources 35 will have a long life span, andthe liquid crystal display's life span can be improved as well.

The ground potential electrodes 35 d and the high voltage electrodes 35c of light sources 35 can be moved in the direction x of FIG. 8A, andthe brightness between the high voltage electrodes 35 c and the groundpotential electrodes 35 d of each of the light sources 35 can beadjusted by such movement. Therefore, a back light unit 300 with uniformside illuminance can be achieved.

<A Resin Frame>

The lower resin frame 500 forms a part of the liquid crystal displaymodule and houses the back light unit 300. Here, the lower resin frame500 has the shape of an open box which only a bottom and sides. Adiffusing plate 60, with which the back light unit 300 is covered formsthe top side. The diffusing plate diffuses light from each of the lightsources 35 of the back light unit 300. As a result, uniform light forwhich brightness is not biased can be irradiated onto the liquid crystaldisplay panel 400. In this case, the thickness of the lower resin frame500 is small. The decreased mechanical strength resulting from the smallthickness can be reinforced by the inner frame 700.

High cycle power supply substrate 40 (for instance, AC/AC invertor)provided to supply the high cycle voltage to light sources 35 isinstalled in the back of this lower resin frame 500. The wiring fromthis high cycle power supply substrate 40 is connected with thehigh-pressure side electrode and earth side electrode of each of thelight sources 35.

FIG. 10 is a perspective view illustrating the resin frame 500 of theback light unit. The lower resin frame 500 has projections 500A, whichproject in parallel at each vicinity and extend in the direction x, andside parts 500B. The lower resin frame 500 and the inner frame 700increase the strength of the module. Moreover, the height of theprojection 500A of the lower resin frame 500 is formed to be higher thanthe height of the high cycle power supply substrate 40. The side part500B is arranged to be adjacent to the control circuit board 10.Therefore, the area of the control circuit board 10, having a complexarrangement of circuit components, can be enlarged. Moreover, the innerframe 700 is formed between the control circuit board 10 and the liquidcrystal display panel 400. That is, the inner frame 700 operates as ashield against electromagnetic waves. The projection 500 is given fulleffect even if it is formed in the direction y.

<The High Cycle Power Supply Substrate>

FIG. 11 shows the underside of the back light unit. The high cycle powersupply substrate 40 has a respective transformer 71 for each of thelight sources 35 of the back light unit 300. It is also possible thatthis transformer 71 is/are formed from one, a couple of 8 tubes, tofour, a couple of 2 tubes. Moreover, the high cycle power supplysubstrate 40 is arranged through a shield board 72, installed at theback of the lower resin frame 500. A part of shield board 72 (formingpart of the high cycle power supply substrate 40) has an open area 72A.The purpose of this is to avoid the generation of an electric current onthe shield board 72 by transformer 71. Moreover, the high cycle powersupply substrate 40 has a wiring layer for the shield. And, a DC/ACinvertor 40 is formed to a height such that it does not protrude aboveprojections 500A.

<An Inner Flame>

The inner frame 700 is arranged between the liquid crystal display panel400 and the diffusing plate (not shown in FIG. 2). The inner frame 700has an open side 42 formed in the display area of the liquid crystaldisplay panel 400 and is composed of a thin metallic board. The lowerresin frame 500 is fixed via a diffusing plate on the inner frame 700. Aspacer 44 for positioning the liquid crystal display panel 100 is formedon a part of the inner frame 700 where the liquid crystal display panel400 is mounted. As a result, the liquid crystal display panel 100 can bearranged on the inner frame 700 at an accurate position. And, the innerframe 700 has sides 46 united with each other. That is, the open side 42is arranged at the inner frame 700 with the bottom formed of a metallicfloor of the box.

A diffusing plate is arranged between the inner frame 700 and the lowerresin frame 500. The inner wall of side 46 of the inner frame 700 isopposed to the outside wall on the side of the lower resin frame 500.The inner frame 700 becomes part of the back light unit along with thelower resin frame 500. The mechanical strength can be improved withoutenlarging the thickness of the lower resin frame 500. That is, the innerframe 700 and the lower resin frame 500 have an improved mechanicalstrength and a strength against a diagonal twist. Moreover, theprojection 500A contributes a resistance to diagonal twist too. As aresult, the display area of a liquid crystal display can be wider andstill maintain enough strength. Moreover, the mechanical strength of theinner frame is better and the handling of the module is easier than in amodule in which the frame has a narrow side.

In embodiment 2,a control circuit board 10 and DC/DC converter substrate11 are arranged on side 46 of the inner frame 700. As a result, thedisplay area of the liquid crystal display panel 400 can be expanded.The control circuit on the circuit board 10 is connected respectivelythrough the flexible printed gate circuit 15, the flexible printed draincircuit 16A, 16B, and a connection port 18, 19A, and 19B. As a result,the electromagnetic waves generated from the control circuit can beshielded from other circuits.

<An Upper Frame>

The upper frame 800 has the function to fix the liquid crystal displaypanel 400, the inner frame 700, and the diffusing plate with the lowerresin frame 500. A liquid crystal display module is composed of theupper frame 800 and the lower resin frame 500 and intervening elements.The upper frame 800 has open side 48 which corresponds to the displayarea the liquid crystal display panel 400. Moreover, the upper frame 800functions as a shield against EMI.

FIG. 12 is the front view and FIGS. 12( a) to 12(d) are side views ofthe liquid crystal display panel. The lower resin frame 500 hasprojections 500A which function to increase panel strength.

FIG. 13 is a sectional view of the liquid crystal display panel of anembodiment 2 as seen on the line 8 b-8 b of FIG. 8A. The embodiment 2differs from embodiment 1 in that the back light unit 300 is coveredwith a diffusing plate 50, and an electromagnetic shield board 51 isarranged on the liquid crystal display panel unit 400 side of thediffusing plate 50. The shield board is for shielding theelectromagnetic waves generated from light sources 35 of the back lightunit 300. For instance, the electromagnetic shield board 51 is made of atransparent conductive sheet or a metallic mesh. As a result, EMI(electromagnetic wave interference) of light sources 35 driven with thehigh cycle voltage can be prevented. And, a reflector 36 made of ametallic material also can prevent EMI.

A diffusing plate 52 is arranged on the liquid crystal display panelunit 400. As a result, the light irradiation onto the liquid crystaldisplay panel unit 400 from the back light unit 300 becomes more uniformdue to the presence of the diffusing plate 52 and the diffusing plate50. Either the lower resin frame 500 or the reflector 36 may be made ofa metallic material and be covered by the electromagnetic shield board51 for completely shielding against EMI.

FIGS. 14A, 14B, and 14C are a sectional views of a lamp tube in a backlight unit according to an embodiment 3. In FIG. 14A, an electrode ofthe light sources 35 has a ring shape and is formed on a discharge tube.A section along line 14 a(1)-14 a(1) is shown in FIG. 14A(1). In FIG.14B, the electrode is formed partially around the discharge tube. Asection along line 14 b(1)-14 b(1) is shown in FIG. 14B(1). In FIG. 14C,the electrode is a ring shape and has an interval or space between theelectrode and the discharge tube. A section along line 14 c(1)-14 c(1)is shown in FIG. 14C(1).

FIGS. 15A, 15B, 15C and 15D are diagrams illustrating various electrodearrangements of the lamp tube according to an embodiment 4. FIGS. 16A,16B, 16C and 16D are diagrams illustrating further electrodearrangements of the lamp tube according to embodiment 4.

The ground potential electrode 35 d and the high voltage electrode 35 care formed at opposite ends of a discharge tube in FIG. 15A. The lengthof the discharge tube 35 a is limited, but a light source 35 canfunction by itself by increasing the voltage of the power supply.

FIG. 15B shows a single high voltage electrode 35 c formed at the centerof a discharge tube 35 a and the ground potential electrodes 35 d formedat each end.

In FIG. 15C, the ground potential electrodes 35 d are formed at thecenter of a discharge tube 35 a and both ends, respectively, and thehigh voltage electrodes 35 c are formed between respective pairs ofground potential electrodes 35 d.

FIG. 15D shows a single ground potential electrode 35 d formed at thecenter of a discharge tube 35 a and the high voltage electrodes 35 cformed at opposite ends.

FIG. 16A shows high voltage electrodes 35 c formed at the center of adischarge tube 35 a and at both ends of the tube, and the groundpotential electrodes 35 d formed respectively between pairs of the highvoltage electrodes 35 c.

FIG. 16B shows the ground potential electrodes 35 d formed at the centerof a discharge tube 35 a and both ends, respectively, and the highvoltage electrodes 35 c formed between respective ground potentialelectrodes 35 d, with the ground potential electrode 35 d at the centerbeing divided into two spaced electrodes.

FIG. 16C shows a ground potential electrode 35 d formed at the center ofa discharge tube 35 a, and high voltage electrodes 35 c formed at eachend, with the ground potential electrode 35 d at the center beingdivided into two spaced electrodes.

FIG. 16D shows high voltage electrodes 35 c formed at the center of adischarge tube 35 a and at both ends, respectively, and ground potentialelectrodes 35 d formed between respective high voltage electrodes 35 c,with each ground potential electrode 35 d being divided into two spacedelectrodes.

The electrode at least needs to couple the ground potential electrodes35 d and the high voltage electrodes 35 c. And, the number of electrodesis selected according to the length of a discharge tube and/or thevoltage of the power supply.

FIGS. 17A, 17B and 17C are diagrams illustrating electrode arrangementsof the lamp tube according to an embodiment 5. FIG. 17A corresponds ingeneral arrangement to FIG. 15A, FIG. 17B corresponds in generalarrangement to FIG. 15B, and FIG. 17C corresponds in general arrangementto FIG. 16B.

The ground potential electrodes have an assistance electrode 70 whosewidth is smaller than the electrodes 35 d, and the assistance electrodes70 are formed adjacent the ground potential electrodes 35 d. When theground potential electrodes 35 d and the high voltage electrodes 35 care discharged, an assistance electrode 70 prevents a brightnessincrease in the direction x. The assistance electrode is available toform two or more. The assistance electrode 70 will cause the electricaldischarge of the lamp to be uniform by adjusting the minuteness in thedirection x.

FIG. 18 is an exploded perspective view illustrating the back light unitof an embodiment 6. The main difference from the embodiment of FIG. 4 isin the bending of the discharge tube 35 a. In this regard, the dischargetube 35 a is composed of one consecutive tube.

Using the discharge tube 35 a which is wound back and forth, it ispossible to reduce the number of tubes used for display panel, since theamount of the light irradiation is larger than that of a straight tube.As a result, manufacturing and assembly become easy. FIG. 19 showsanother embodiment in which two or more discharge tubes 35 a are woundin pairs.

According to these embodiments, the liquid crystal display unit has alife span which is increased without the need to replace the lamp tubeor the back light unit. Concretely, the electrodes of the light sourcewhich control the liquid crystal display according to this invention arearranged outside the tube, whereby the consumption of mercury inside thetube is reduced.

1. A liquid crystal display device comprising: a liquid crystal displaypanel which has a first drain lines group including a plurality of drainlines and a second drain lines group including a plurality of drainlines; a control circuit board which has a control unit; a first draindrivers group which has a plurality of drain drivers and is connected tothe first drain lines group; a second drain drivers group which has aplurality of drain drivers and is connected to the second drain linesgroup; a back light unit which is arranged at a back side of the liquidcrystal display panel and has a light source; a metal frame; and ashield member which shields against EMI; wherein both of the first draindrivers group and the second drain drivers group are arranged at a sameperipheral side of the liquid crystal display panel; wherein the controlunit supplies a first signal to only the first drain drivers group via afirst flexible printed circuit; wherein the control unit supplies asecond signal to only the second drain drivers group via a secondflexible printed circuit; wherein the first flexible printed circuit andthe second flexible circuit are connected to the control circuit board;wherein the control circuit board is sandwiched between the metal frameand the shield member; and wherein the metal frame is arranged betweenthe control circuit board and the liquid crystal display panel.
 2. Aliquid crystal display device according to claim 1, wherein the firstflexible printed circuit is a single flexible printed circuit andcorresponds to the plurality of drain drivers of the first drain driversgroup; and wherein the second flexible printed circuit is a singleflexible printed circuit and corresponds to the plurality of draindrivers of the second drain drivers group.
 3. A liquid crystal displaydevice according to claim 1, wherein the control circuit board has afirst connection port which is connected to the first flexible printedcircuit and a second connection port which is connected to the secondflexible printed circuit; and wherein the control unit is arrangedbetween the first connection port and the second connection port.
 4. Aliquid crystal display device according to claim 1, wherein the controlcircuit board has a first connection port which is connected to thefirst flexible printed circuit and a second connection port which isconnected to the second flexible printed circuit; and wherein a distancebetween the first connection port and one of the plurality of draindrivers of the first drain drivers group is substantially equal to adistance between the second connection port and one of the plurality ofdrain drivers of the second drain drivers group.
 5. A liquid crystaldisplay device according to claim 1, wherein the metal frame is arrangedbetween the control circuit board and the light source.
 6. A liquidcrystal display device according to claim 1, wherein the plurality ofdrain lines of the second drain lines group are different from theplurality of drain lines of the first drain lines group; wherein theplurality of drain drivers of the second drain drivers group aredifferent from the plurality of drain drivers of the first drain driversgroup.